Check with the shop installing your hitch and see if they can do an electric brake controller and install a 7 way (RV style) connector on your pickup, and show you how to use it. Often you can buy a harness made to "T" into your vehicle's wiring.
If your truck is a manual transmission cooling should be ok if the system is in good order (clean radiator, fresh coolant, clean A/C condenser rad, fan drive functioning properly etc). If it is an auto trans consult your manual and see if an auxiliary trans cooler is recommended.
edit: oh and if you have a topper on the pickup bed your 22R engine will enjoy towing your trailer much better - it makes for more efficient aerodynamics.
Enjoy your Casita.